A woman who allegedly extorted more than $90,000 from an elderly man after befriending him and stealing his Pin is one of a spate of similar cases under investigation in Hamilton.

It has sparked a police warning for families, relatives and friends of senior citizens to be vigilant around credit card security.

They have received numerous complaints around issues of caregivers obtaining, by various means, Pins and allegedly using them to extract cash, communications manager Andrew McAlley said.

In one case, a 29-year-old woman is alleged to have extorted $90,000 from a man in his eighties after befriending him in a neighbourly way.

It appeared to start with her taking the man shopping to the supermarket.

"She progressively gained his confidence and then gained access to the victim's Pin. This came to light after some good old-fashioned police work and intuition," McAlley said.

The case remains under investigation.

Financial abuse, as Age Concern Hamilton chief executive Gail Gilbert described it, makes up half of all elder abuse.

It's always high on their agenda and it happens in various ways.

"It's family members who are abusing mum and dad's money and that's either through access to eftpos cards or Pin numbers and then using it for their own ends. Or it can be material assets they are abusing. It could be an abuse of enduring power of attorney where someone's got the decision-making responsibility for an older parent who has lost the ability."

National Age Concern figures show reported referrals of financial elder abuse almost doubled from 1100 in the 2010-11 financial year to about 2000 in 2012-13.

Relatives and friends are also urged to report suspected elder abuse to Age Concern. Co-ordinators can help people navigate their way out of an abusive situation and very few cases end up in legal proceedings or court. Support and counselling for both the abused person and the abuser are available.

Gilbert said older people often want to help family members out financially and their advice is do it legally and record it. Don't just hand money over and expect it to be repaid.

"There are cases where an older adult has been deliberately targeted by someone who befriends them, moves into their house and becomes their carer but really with the sole purpose of getting access to their money and ripping them off."

Older people can be very trusting and often don't realise there's a hidden agenda, Gilbert said.

"They can also be pleased that someone is taking an interest in them. They may have no family and have been living alone for years."

In many cases it's neighbours, or others close to the elderly person, who report situations to Age Concern.

In another case, McAlley said a man contacted police in relation to his 60-year-old father who was in hospital with a brain injury.

"His former partner, a 34-year-old woman, is believed to have visited him in hospital and staff noticed the woman taking the man out for a stroll. And we believe, subsequent to that, that his card has allegedly been used to make a number of cash withdrawals and purchases. What we're finding is a number of instances of caregivers or people on the periphery gaining an elderly person's confidence and getting their Pin numbers."

Age Concern chief executive Robyn Scott Elder said abuse can take many forms. Sometimes there are several types occurring in the same situation.

"For example, if a person is threatened that they won't see their grandchildren if they don't hand over money, that's both psychological and financial abuse.

"In the cases we've seen at Age Concern over the past three years, three-quarters involved psychological abuse such as threats, humiliation, or preventing people making decisions for themselves. In over half the cases we saw there was an element of financial abuse."

Elder said stealing and scams are obviously financial abuse but it also happens in more insidious and subtle ways.

"As an example, family members may move in with an older parent to save on accommodation costs, and the parent ends up paying all the family's expenses.

"That might start out being OK, but over time the older person may start feeling anxious as they see their savings diminish while the financial demands continue."

A good way to curb the problem is to install daily credit limits on cards, McAlley said.

Police are also noticing the vulnerabilities of contactless payment cards.

In particular, McAlley said people putting their handbags or wallets in shopping trolleys have been stolen.

"We're emphasising that people should have one hand on their handbag at all times in the supermarket.